A working machine, such as a forklift truck, is provided with a load handling interlock mechanism which includes a seat switch which detects whether an operator has left the seat, or not. When the seat switch detects a seat leaving (OFF), or the key switch is brought into OFF, the load handling interlock mechanism brings a work device, such as a fork, which is hydraulically driven, into a locked state (refer to Japanese Laid-open Patent Publication No. 2009-19660).
This conventional load handling interlock mechanism is configured such that the locked state of the work device is released when the key switch is ON, and the seat switch is ON (detection of seating). The load handling interlock is configured to be able to be released under such a releasing condition because, even when the engine is stopped due to a malfunction of the working machine or a fuel shortage and the like, the work device can be moved by operating the work operation lever so that the working machine can be safely brought down.
On the other hand, some ordinary vehicle is provided with an auto idle stop mechanism which automatically brings the idle rotation state of the engine into the stop state when a predetermined time elapses after the above-mentioned seat switch is brought into OFF.